The present invention relates to regulating the output voltage of adaptive power supplies, switching power converters, and similar pieces of equipment within tightly-controlled specifications. The disclosed remote regulation system achieves highly accurate output voltage which is required for high-reliability systems. Specifically, one embodiment of the invention relates to a system and method for regulating a switching power converter operating relative to a local ground, where the input for the regulation loop is a line voltage measurement taken at a point where the relative line ground may be different than the local ground. Typically, the line voltage measurement is taken from a position that is quite remote from the power converter. One method disclosed herein for maintaining the line voltage within tightly-controlled parameters is to compare the line voltage with a known reference voltage relative to the line ground where the line voltage measurement is taken. The resultant error signal, which is relative to the line ground is then translated to a control signal which is relative to the local ground. The control signal is then applied to the power converter to thereby control the power converter, and hence the remote line voltage, with precision not achievable with prior art regulation systems and methods.
Prior art systems and methods either cannot achieve tight control of output voltage from a power supply at a remote location or must use a complex power distribution design, thereby increasing the cost of the system, in order to maintain the required output voltage within specific design parameters. It is to be understood that the term xe2x80x9cpower supplyxe2x80x9d as used herein may relate to any type of electrical power supply such as, but not limited to, adaptive power supplies, switching power converters, and power conditioning units. The invention is in no way limited to a particular xe2x80x9cpower supplyxe2x80x9d.
As used herein, remote power supply regulation refers to sensing the output voltage from a power supply at a remote location. xe2x80x9cRemote locationxe2x80x9d should be understood to mean anywhere where the measured line voltage is relative to a line ground that may be different than the power supply ground. Typically, the line ground is different, i.e., xe2x80x9cfloatsxe2x80x9d, relative to the power supply ground where the line voltage measurement is taken at a large distance from the power supply, such as at the end of long cables that are attached at the other end to the power supply to be regulated. The internal line resistance in long cables is a typical cause for the line ground at the voltage measurement point to be different than the power supply ground. However, anywhere where the line ground at the point of line voltage measurement may be different than the power supply ground may be a xe2x80x9cremote locationxe2x80x9d as defined herein.
A typical prior art solution to remote power supply regulation comprises a remote sense amplifier and an error amplifier connected to a reference voltage. Typically, but not necessarily, the remote sense amplifier and the error amplifier are physically located near the power supply to be regulated. Therefore, it is convenient to have the reference voltage relative to the local ground, i.e., power supply ground. Such a design requires that the voltage being compared to the reference voltage be relative to the same ground to which the reference voltage is relative. Therefore, typical prior art remote regulation systems first translate the line voltage, which is relative to the line ground, to a voltage that is relative to the power supply ground via the remote sense amplifier. After the measured line voltage is converted, the resultant voltage is then compared to the reference voltage via the error amplifier resulting in a control signal relative to the power supply ground. The control signal is then applied to the power supply so as to effect control on the power supply as a function of the measured line voltage.
The remote sense amplifier typically has an input resistor divider network. The resistor divider network adds errors to the measured line voltage signal passing through the network due principally to resistor variations. Additionally, the remote sense amplifier itself adds errors due to offsets and bias currents. Therefore, the voltage produced at the output of the remote sense amplifier is comprised of the translated measured line voltage plus some unknown error voltage. The remote sense amplifier output voltage, including the error voltage, is then applied to the error amplifier for comparison with the reference voltage. The resultant control signal produced by the error amplifier is, in part, a function of the unknown and possibly varying errors in the remote sense amplifier and its input resistor network. These errors have also been amplified by the error amplifier. Consequently, the tolerances that can be achieved by such a prior art system are limited by the introduction of the errors introduced by the remote sense amplifier and its input resistor network.
As an example, consider the typical prior art design of a remote regulated power supply shown in FIG. 1. Typical for such a device, the worst-case power supply voltage accuracy of 3.3 volts xc2x14% at the remote sensing point (Vout) is achievable. If one component in an operating system which is supplied by the power supply of FIG. 1 requires that its supplied voltage be within xc2x15% of nominal, then the power distribution losses from the remote sense point must be less than 1%. If the operating system requires a total power supply current of 3.3 volts at 100 amps, a 1% variance is equivalent to 33 mV or 330 micro ohms. Such tight tolerances require a complex, and very expensive power distribution design as well as precision components.
The present invention overcomes the limitations of the prior art by placing the error amplifier, with a reference voltage relative to the line ground, upstream of the remote sense amplifier. This configuration avoids amplifying the unknown errors produced by the remote sense amplifier due to offsets and bias currents. The inventive design significantly improves the accuracy achievable by the remote regulator.
Accordingly, it is an object of the present invention to obviate many of the above problems in the prior art and to provide a novel system and method for the remote regulation of a power supply, such as, for example, an adaptable power supply or a switching power converter
It is another object of the present invention to provide a novel system and method for producing a control signal responsive to the difference between the magnitude of an attribute of a first signal with the magnitude of an attribute of a second signal.
It is yet another object of the present invention to provide a novel system and method for maintaining the line voltage between two terminals that are connected to but remote from a power supply where the voltage between the line ground and the power supply ground is non-zero.
It is still another object of the present invention to provide a novel system and method for maintaining the line voltage between two terminals that are connected to but remote from a power supply where the electrical potential of the line ground is greater than the electrical potential of the power supply ground.
It is a further object of the present invention to provide a novel system and method for producing a control signal responsive to the line voltage between a first and second signal where the line voltage is compared to a reference voltage to produce an error voltage and the error voltage is compared to the voltage between the line ground and a local ground so as to translate the error voltage from being relative to the line ground to being relative to the local ground to thereby produce a control signal responsive to the line voltage.
It is yet a further object of the present invention to provide a novel system and method for controlling the output of an adaptable power supply including a remote sense feedback amplifier in series with an error amplifier where the remote sense feedback amplifier is downstream of the error amplifier.
It is still a further object of the present invention to provide a novel system and method for regulating the output of an adaptive power supply as a function of a line voltage measure between a pair of conductors connected to the power supply at a point where the voltage between the ground reference at the point of the line voltage measurement and the ground reference at the power supply is non-zero.
It is an additional object of the present invention to provide a novel system and method for regulating the output of an adaptive power supply at a second ground including measuring the line voltage relative to a first ground, comparing the line voltage with a reference voltage relative to the first ground to produce a first error voltage relative to the first ground, translating the first error voltage to a second error voltage relative to the second ground, and applying the second error signal to the adaptive power supply to regulate the power supply as a function of the line voltage.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.